(1). Field of the Invention
This invention relates to a dual or sandwich belt conveyor system in which material to be conveyed, which is placed between two superimposed conveyor belts, is conveyed in the direction of from the lower part to the upper part of the conveyor system, or in the reverse direction, and particularly a dual belt conveyor system in which work for adjusting edge rollers brought into contact with belt edges of two superimposed conveyor belts can be made easily, and maintenance efficiency of rollers disposed in a looped part of the dual belt conveyor system can be improved.
(2). Description of the Prior Art
A dual belt conveyor system is known in which material to be conveyed, for example, massive material such as ore and limestone, granular material typified by beans, and powdery material such as sugar and flour, and other material with various properties, is conveyed in the vertical direction by being placed between two superimposed conveyor belts. In this dual belt conveyor system, higher tensile force, as compared with an ordinary conveyor system, is applied to two superimposed conveyor belts so that material to be conveyed can be carried between two superimposed conveyor belts by exerting a force on the conveyor belts which tends to force each belt into contact with the other.
Carrier rollers are arranged in horizontal conveying parts disposed at the upper part and at the lower part of the conveyor system, respectively, and looped conveying parts are connected to the respective horizontal conveying parts with a vertical conveying part so that one conveyor belt or two superimposed conveyor belts are supported by the carrier rollers. In a different embodiment, a plurality of edge rollers are arranged in a vertical conveying part so that two superimposed conveyor belts are supported by the edge rollers, which are brought into contact with both lateral belt edges of two superimposed conveyor belts.
The above-mentioned edge rollers are staggered against and brought into contact with both lateral belt edges in the vertical conveying part in such a manner that the material-carrying surface areas of two conveyor belts (namely surface areas of two superimposed conveyor belts which confront each other and carry material to be conveyed therein) move in essentially the same straight line. Therefore, with conveyor belts being worn away, edge rollers are apt to leave both lateral belt edges of conveyor belts and sufficient support of conveyor belts, therefore, becomes impossible. In this case, it is necessary to adjust the position of individual edge rollers in such a manner that each roller is brought into contact with the conveyor belts.
However, adjusting individual edge rollers in such a manner that each individual roller is brought into contact with conveyor belts is very time consuming, since the number of the above-mentioned edge rollers abounds in a vertical conveying part (in the case of the height of a vertical part being 15 m, the number of edge rollers is about 240). In order to solve this problem, Japanese utility model laid-open No. 42967 of 93 (Heisei 5) is provided. This art discloses a pair of parallel frames, in which these frames are moved relatively in opposite direction of each other so that adjustment is made in which individual rollers mounted on the frames are brought into contact with the conveyor belts.
In the above-mentioned art, where new conveyor belts are used, individual edge rollers can be brought into contact with the conveyor belts at nearly equal spaces in the direction of belt travel. However, when conveyor belts are worn away, spaces between edge rollers in the direction of belt travel become varied and the conveyor belts are not supported uniformly at nearly equal spaces. In this case, material to conveyed leaks from the lateral belt edges of the two traveling superimposed conveyor belts.
Further, since the outer surface of used carrier rollers for supporting belts become worn, a change of worn rollers for new rollers is needed. When worn carrier rollers are changed for new rollers, it is first necessary to remove a base plate on which a stand for bearing each individual carrier roller is fixed from an apparatus frame (not shown). This work is carried out by first removing bolts for fixing the base plate and, thereafter, removing the base plate from the apparatus frame with the base plate being laid on the side. However, since this work is difficult, various arts are proposed.
In carrier rollers disclosed, for example, in Japanese utility model laid-open No. 50214 of 1989 (Showa 64), each individual carrier roller is supported on a roller frame which is formed individually, and each individual roller frame is secured to a base frame, so that carrier rollers can be easily exchanged by removing each carrier roller individually. Further, as disclosed in Japanese utility model laid-open No. 145222 of 1990 (Heisei 2), a foundation part is put over the conveyor belts in the lateral direction of the belts, an inner supporting part for supporting the center rollers is secured to the foundation part, and an outer supporting part for supporting the outside of the slide roller is detachably attached to the foundation part.
The above-mentioned arts relate to carrier rollers used for dual belt conveyors in which material such as ore is placed and conveyed on one continuously traveling belt. In the case where the carrier rollers are exchanged, loads which act on carrier rollers are nearly equal to the sum of the weight of the belt portion between adjacent carrier rollers and the weight of the material to be conveyed which is placed on the belt portion, in which burden loads acting on carrier rollers are not so heavy. Accordingly, an exchange of used carrier rollers for new carrier rollers can be easily made by supporting the lower part of the belt by other supporting members.
However, since high tension acts on both belts in a dual belt conveyor, loads according to the tension applied to the belt by the weight of the material to be conveyed act on carrier rollers which are disposed on a circular arc forming a looped conveying part. Therefore, when exchanging carrier rollers, it is necessary to apply a force in the normal direction of the loop forming the looped conveying part to two conveyor belts by means of a chain block. Accordingly, problems arise relating to the strength which is caused by applying partial tension to belt, and a decrease in the working efficiency of exchange of carrier rollers.
Further, even when carrier rollers in accordance with the conventional art are applied to a looped conveying part having the above-mentioned problems, the above-mentioned problems are solved. Namely, since in conventional carrier rollers an axis has two chamfered parts formed on a part of the axis in the longitudinal direction, and the roller stand has on the upper end side thereof a groove with the same length as the above-mentioned two chamfered parts, it is necessary to insert a part of the axis with the two chamfered parts into the groove from the upper end of the roller stand, and is, therefore, also necessary to raise the axes to a higher position than the upper end of the roller stand. Therefore, there is the problem that it is also necessary to apply a force in the normal direction of the loop forming the looped conveying part to two conveyor belts by means of, for example, a chain block.